1. Field of the Invention
The present invention generally relates to the field of resolution enhancement technologies (RET), and more particularly to a method of optical proximity correction (OPC).
2. Description of the Prior Art
With the trend of miniaturization of electronic products and peripheral devices, research into thin structures and high integration of semiconductor devices has become a main concern in the industry. Lithography technology plays an important role in determining the performance of semiconductor devices.
In semiconductor manufacturing processes, an integrated circuit layout is first designed in an IC-design house and formed as a mask pattern. The mask pattern is then proportionally transferred to a photoresist layer disposed on the semiconductor wafer through an exposure process followed by a development process. Subsequently, a corresponding etching process is performed in order to manufacture the semiconductor devices on the semiconductor wafer. With the demand of increasing integration of semiconductor devices, the design rule of line width and spaces between lines or devices becomes finer. However, due to the optical proximity effect (OPE), the width is subject to optical limitations. To obtain the fine-sized devices, the pitch i.e. the interval between transparent regions in a mask, is scaled down along with the device size. However, if the pitch is scaled down to a specific range (for example, equal to or smaller than half the wavelength of light used in the exposure process), diffraction and interference may be inevitable when the light passes through the mask. The resolution of the mask pattern transferred onto the photoresist layer will be affected; due to the OPE, deviations in the transferred pattern such as rounded right-angle corners, shortened line-ends, or increase/decrease of line widths may occur.
To overcome the above problems, several resolution enhancement technologies (RET) have been studied and commercialized recently. In detail, one of the most common methods adopted by the semiconductor manufacturers is an optical proximity correction (OPC) method. The OPC method is a simulation and correction method in which lines width and/or contours of feature patterns in the individual design layout are properly corrected. After the OPC process, the corrected feature patterns in the individual design layout may be outputted to a mask-making system in order to manufacture the corresponding photomask.
Although the OPC method has been widely adopted by the semiconductor manufacturers and successively overcome major drawbacks in the fabricating process, there are still some problems needing to be solved. During the OPC process, each feature pattern, such as a polygon, in the design layout is often fragmented by dividing the edges of the polygon into several edge segments. However, when the same edges of the polygon are corrected (or fragmented) by two independent OPC processes, the corresponding two edge segments are often mismatched in the following merging process and the elimination of this mismatch is time-consuming and costly. Therefore, how to effectively solve this problem is still a major topic for study in the semiconductor field.